Secretory IgA

Test Indications:

Test Summary:

Testing for secretory IgA production in the bowel

The gastrointestinal tract serves a vital function by excluding the uptake of bad bacteria and pathogens, which is accomplished in large part by the antigen binding activity of the immunoglobulin secretory IgA (sIgA). sIgA acts almost like a sponge soaking up things that can harm the gastrointestinal lining. The humoral immune status of the GI tract can be assessed by determining the fecal concentration of sIgA. The sIgA secreted by mucosal-associated lymphoid tissue, represents a pivotal and specific line of defense of the GI mucosa, along with such non-immune factors as mucins and lactoferrin. As the principal immunoglobulin isotype present in mucosal secretions, sIgA plays an important role in controlling the intestinal environment, which is constantly presented with potentially harmful antigens such as pathogenic microorganisms, abnormal cell antigens, and allergenic proteins.

Secretory IgA has been shown to bind to toxin A from Clostridium difficile, preventing its interaction with the brush border of the intestines. Other studies indicate that sIgA prevents Vibrio cholera from adhering to the intestinal mucosa. These bacteria agents cause infectious diarrhea.

Deficiencies in sIgA have been associated with increased absorption of food protein antigens as well as with lowered resistance to intestinal infection, including yeast overgrowth. In instances where sIgA is low, there is increased risk for adhesion and proliferation of pathogenic organisms, and for associated damage to the intestinal mucosa. Levels higher than reference range have been associated with atopic dermatitis, dysbiosis, increased exposure to pathogenic organisms and toxins, and increased exposure to allergens.